As shown in FIG. 1, a conventional plane display apparatus based on a STN (super twist nematic) method is constituted in such a manner that a liquid crystal 3 is filled between substrates 2a and 2b provided with ITO electrodes 1a, 1b thereon and oriented films 4a and 4b are formed between the ITO electrodes 1a,1b and the liquid crystal 3.
Further, in the case of a color display apparatus, a color filter 5 is formed between the ITO electrode 1a and the substrate 2a.
In such a display apparatus based on the STN method, if a certain level of voltage is supplied between the two ITO electrodes 1a, 1b and the liquid crystal 3 disposed between the two electrodes 1a and 1b are driven in order for the liquid crystal 3 to be oriented in a certain direction by the oriented films 4a and 4b, the color of the color filter 5 at the portion of the ITO electrodes 1a and 1b on which the voltage is supplied displayed after the passing-through of light rays.
However, in such a display apparatus based on the STN method, the color filter 5 is formed between the substrate 2a and the ITO electrode 1a, and the oriented films 4a and 4b are formed between the ITO electrodes 1a,1b and the liquid crystal 3 as described above.
Therefore, the processes for forming the color filter 5 and the oriented films 4a and 4b have to be added, thereby complicating the process.
In an attempt to overcome the above described disadvantages, a display apparatus based on a PDLC (Polymer Dispersed Liquid Crystal) method as shown in FIG. 2 has been developed, and according to this method, liquid crystals dyed with red, green and blue (R, G and B) colors are used, so that the process should be simplified.
That is, a macro polymer 11 and liquid crystals 12 which are respectively dyed with R, G and B colors are physically mixed together so as to form a uniform mixture so that ultraviolet rays are irradiated on the mixture.
Then, the polymer 11 undergoes a polymerization so as to be solidified, while the liquid crystals 12 of the R, G and B colors are maintained in the original state. Under this condition, the existence of the R, G and B liquid crystals 12 in the form of small drops within the polymer 11 is utilized, and this arrangement is disposed between substrates 14a and 14b on which ITO electrodes 13a and 13b are formed.
In such a display apparatus based on the PDLC method, when no voltage is supplied to the two ITO electrodes 13a and 13b, the small drops of the liquid crystals 12 take random directions, and therefore, light rays can not pass through due to a dispersion phenomenon. On the other hand, if a certain level of voltage is supplied to the ITO electrodes 13a and 13b, the small drops of the liquid crystals 12 are oriented in the direction of the applied voltage, so that light rays can pass through.
However, the R, G and B liquid crystals 12 are uniformly mixed within the polymer 11 without segregation, and therefore, it is difficult to obtain the respective color characteristics of the crystals. Further, in driving the R, G and B liquid crystals 12 respectively, the voltage and its frequency supplied to the ITO electrodes 13a and 13b have to be different depending on the respective colors, and therefore, the arrangement of the circuit for driving the liquid crystals becomes very complicated, as well as requires an expensive IC for developing the circuit.
Further, as shown in FIG. 2B, the voltage is supplied to the ITO electrodes 13a and 13b which are crossing each other, and therefore, not only are the mutually crossing electrodes 13a and 13b influenced by the applied voltage, but also the adjacent regions as well. As a result, the adjacent regions are driven together and a color dispersion phenomenon occurs, thereby deteriorating the color characteristics.